Interlocking means for series-multiple switch and tap changer in dual rated transformer



Oct. 19, 1965 K. H. SICKLER INTERLOGKING MEANS FOR SERIES 3,213,223 MULTIPLE SWITCH AND TAP CHANGER IN DUAL RATED TRANSFORMER Filed April 29, 1965 2 Sheets-Sheet l K612726272 EPb/fkg xi j m;

Oct. 19, 1965 K. H. SICKLER 3,213,223

INTERLOCKING MEANS FOR SERIES-MULTIPLE SWITCH AND TAP CHANGER IN DUAL RATED TRANSFORMER Filed April 29. 1965 2 Sheets-Sheet 2 BUSH/N6 flgj RIM M6 3A.

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United States Patent 3,213,223 INTERLOCKlNG MEANS FDR SERIES-MULTIPLE SWiTtIl-l AND TAR Cl-IANGER lN DUAL RATED TRANSSFORMER Kenneth H. Sickler, Laneshoro, Mass, assignor to General Electric Company, a corporation of New York Filed Apr. 2), 1963, Ser. No. 276,494 3 Claims. (Cl, 200-50) This invention relates to interlocking means and more particularly to an interlocking means for a series-multiple switch and a tap changer in a dual voltage rated transformer.

As is well known to those skilled in the transformer art, it is a common practice to provide transformers which have a dual voltage rating. In general, the term dual voltage rating is applied to transformers which are provided with a low voltage setting and a high voltage setting. It may be that more than two different voltage ratings are provided such as, for example, a plurality of high voltage ratings and a single low voltage rating. However, the transformers are designated as dual voltage rating transformers" and it will be understood that the term dual voltage rated transformer as used throughout this specification and claims will relate to transformers which are provided with a high voltage rating and a low voltage rating, although there may be more than one low voltage rating and more than one high voltage rating for such transformers. In general, the dual voltage of the dual voltage rated transformer is provided by means of a multiple primary winding which may be connected in either series or in parallel to provide the desired voltage rating for the transformer. For example, a transformer may be provided with a plurality of 2400 volt windings. When these windings are connected in parallel the voltage rating of the transformer will be 2400 volts. However, when the windings are connected in series the transformer will have a voltage rating according to the number of 2400 volt windings which are provided to the transformer. For example, when three windings are provided the voltage rating would be 7200 volts. As will be apparent, by use of a series-parallel switch, which is generally referred to in the art as a series-multiple switch, and will be so designated throughout this specification and claims, the rating of the transformer can be changed from either the low voltage to the high voltage rating, as desired.

In many instances, utilities have required that their dual voltage transformers be provided with alternate high voltage ratings. In other words, many utilities require that their dual voltage rated transformers be provided with high voltage ratings which may vary over a specified range. For example, one such transformer may have a low voltage rating of 2400 volts and be provided with a high voltage rating of either 7200 volts or 7970 volts. Utilities require these plurality of high voltage ratings because in many instances utilities have different areas having different high voltage rating requirements. In order to minimize the various types of transformers which the utilities are required to stock, they generally require that a single transformer be available which will be useful for either of their high voltage rating requirements.

In order to provide the desired dual voltage rating transformer having a plurality of high voltage ratings it is necessary that either a series-multiple switch having more than two positions be provided, which has two separate high voltage positions, or else that a tap changer be provided for use with the high voltage rating. As will be readily understood, a special series-multiple switch provided with a plurality of hi h voltage settings is a necessarily expensive switch. Therefore, in order to limit the cost of dual voltage rating transformers it is preferred to utilize a tap changer to vary the high voltage Patented Oct. 19, 1965 "ice rating. However, with the use of a tap changer a special problem arises in that the tap changer may be used when the series-multiple switch is in the low voltage positions. When this occurs, one of the parallel windings will be at an incorrect voltage rating; this would induce a short circuit condition in the transformer causing damage and possible destruction of the transformer. Thus it is desirable to provide a dual voltage transformer of low cost, having a variable high voltage rating, without danger of incorrectly connecting the windings of the transformer when in the low voltage setting.

It is, therefore, one object of this invention to provide a relatively low cost, dual voltage transformer having a variable high voltage rating.

Another object of this invention is to provide a dual voltage transformer in which the variable high voltage rating is provided by means of a tap changer.

A further object of this invention is to provide a dual voltage transformer using a tap changer to vary the high voltage setting of the transformer in which the tap changer is only operative when the transformer is in its high voltage operating position.

A still further object of this invention is to provide a dual voltage transformer in which a tap changer is used to vary the high voltage rating of the transformer, and in which means are provided to place the tap changer in its proper position whenever the transformer is placed in low voltage operation.

In carrying out this invention in one form, a transformer is provided having a dual voltage rating, a seriesmultiple switch is provided whereby the transformer may be placed in either a low voltage operation or a high voltage operation. A tap changer is provided, such that the high voltage rating of the transformer may be varied by varying the positions of the tap changer to vary the number of turns in the primary winding of the transformer. An interlocking means is provided between the series-multiple switch and the tap changer such that when the series-multiple switch is in its low voltage operating position the tap changer is in one position and is not movable to any other position. However, when the seriesmultiple switch is in the high voltage operating position the tap changer may be moved to any of its operating positions.

The features of this invention, which are believed to be novel, are set forth with particularity in the appended claims. However, it is believed that this invention and the manner in which its objects and advantages are obtained, as well as other objects and advantages thereof, will be more fully understood by reference to the following detailed description of a preferred embodiment thereof, especially when considered in connection with the accompanying drawings, in which:

FIGURE 1 is a diagrammatic view of the operative members of a series-multiple switch and a tap changer, showing a preferred form of interlocking means according to this invention;

FIGURE 2 is an external view of a transformer tank showing one means of mounting the operating handles of the series-multiple switch and the tap changer;

FIGURES 3A and B are diagrammatic showings of one form of a series-multiple switch which may be used in this invention showing the high and low voltage positions of the switch;

FIGURE 4 is a schematic diagram of one form of the primary windings of a transformer which may be used in this invention; and

FIGURES 5A through C are schematic diagrams of the primary windings, similar to FIG. 4, showing schematically the various connections of the transformer winding which are used to provide the dual voltage rating of the transformer.

In referring to the drawings, like numerals will be used to indicate like parts throughout the various views thereof. FIG. 1 is a diagrammatic showing of the operating portions of a series-multiple switch and a tap changer which may be used in one form of this invention. As is shown in FIG. 1, a series-multiple switch is provided, being operated toeither a high or a low voltage position by means of a handle 12. The handle 12, which is mounted outside of the transformer tank 13, as shown in FIG. 2, operates through a linkage means comprising the rotatable shaft 14 to which the handle 12 is firmly fixed, a linkage member 16 and an operating arm 18. As can be seen from FIG. 1, the operating linkage 16 is securely fixed to both the rotating shaft 14 and the operating arm 18 whereby movement of the handle 12 to either of its two positions causes arm 18 to switch the series-multiple switch to either of its two positions. In order to provide a snap action to the handle 12 of the series-multiple switch a spring member is provided mounted on an arm member 22 which is 'pivotally attached to a lever 24 secured to link 16. As will be understood the spring member 20 and arm 22, which are mounted in a bracket member 26 secured to the transformer tank 13, provide an over-center spring operation. As the handle 12 is moved from the low position shown to the high position link 16 and lever 24 are raised thereby lifting arm 18 which causes spring 20 and arm 22 to move in a clockwise direction about the base of the bracket 26 and forcing lever 24 and link 16 in an upward direction. As will be understood, as the spring 20 and arm 22 move in a clockwise direction, spring 20 is compressed by lever 24. When the spring 20 and arm 22 pass through the dead center position, the spring 20 acts to force lever 24 and link 16 upwardly with a snap action. In the same manner,

when the handle 12 is returned to the position shown,

the spring and arm will move in a counterclockwise direction. When spring 20 and arm 22 pass dead center in a clockwise direction, the lower end 25 of lever 24 is forced upwardly, thereby causing the arm 16 to be drawn downwardly forcing arm 18 into the downward position shown. In this manner, as will be understood, operation of the handle 12 operates the series-multiple switch 10 moving it either to the high or the low voltage position with a snap action by means of spring 20 and arm 22, lever 24 and link 16.

Also as shown in FIG. 1, a tap changer is provided as indicated diagrammatically at which, as will be understood, is used to bridge portions of the primary winding of the transformer. That is, by means of the tap changer 30, the number of turns in the primary winding may be increased or decreased according to the position of the tap changer. The tap changer is operated by means of a handle 32 which is mounted outside the transformer tank 13, as indicated in FIG. 2. As can be seen the handle 32 is firmly fixed to a rotatable shaft member 34 which in turn is fixed to a link 36. An arm member 38 fixed to link 36, depends from the link 36 to tap changer 30 thereby operating the tap changer 30. As will be understood, as handle 32 is moved from the position shown to another position the link 36 is raised, thereby raising arm 38 causing movement of the tap changer. In a similar fashion when the handle 32 is rotated back to the position shown, the link 36 is moved to its downward position thereby forcing arm 38 down and moving the tap changer to the position indicated in FIG. 1.

In order to provide an interlocking means between the tap changer 30 and the series-multiple switch 10 an interlocking arm 40 is provided which connects the link 16 of the series-multiple switch with the link 36 of the tap changer. As will be apparent from FIG. 1, the interlocking arm 40 is firmly fixed at one end to the link 16 of the series-multiple switch and its other end extends through an opening 42 in link 36 of the tap changer. The upper end of the interlock arm 40 is provided with a nut member 44 which prevents arm 40 from returning through the opening 42 in link 36. The length of interlock arm 40, from link 16 to nut 44 is as shown, such that when switch 10 is in the low position, as shown, the nut 44 is against link 36, holding tap changer 30 in the one position, as shown. Thus, when the series-multiple switch 10 is in its low voltage operating position, or moved into such position, the arm member 40 is pulled into the downward position, shown in FIG. 1, pulling link member 36 downwardly and forcing the tap changer into its position shown in FIG. 1. However, when the seriesmultiple switch is moved to its high voltage position the arm member 40 is raised thereby lifting the nut 44 above the link 36 thereby allowing the tap changer to be moved to either of the two shown positions. From the above it will be apparent that when the series-multiple switch is in the low voltage position, shown in FIG. 1, the tap changer is placed in its one position and is held in this position by means of the nut 44 on the arm 40. As long as the series-multiple switch 10 is maintained in the low voltage position the tap changer 30 may not be moved. Of course, it will be apparent that if sufficient force is exerted on handle 32 of tap changer 30, the tap changer may be moved from position 1 to position 2. However, such movement of the tap changer would act through link 36, arm 40 and link 16 to move switch 10 into its high position. Thus the interlock means will positively prevent movement of the tap changer 30 to its 2 position while the series-multiple switch 10 is in its low voltage position.

However, when the series-multiple switch 10 is moved to the high voltage position, arm 40 is raised, thereby raising nut 44 away from link member 36, thereby allowing the tap changer to be moved to either of its two positions, as desired. Thus, as can be seen, by means of the interlocking means set forth herein the tap changer is placed in the desired position whenever the seriesmultiple switch is placed in a low voltage position. However, when the series-multiple switch is moved to the high voltage position it is then possible to place the tap changer in either of its two desired positions.

Referring now to FIG. 3 of the drawings there is shown a diagrammatic presentation of the series-multiple switch 10. As can be seen from FIG. 3A when the series-multiple switch is in the low voltage position, terminals 4, 6 and 2 of the primary winding are connected to the high voltage bushing. In the same manner, terminals 1, 3 and 5 of the primary are connected to the ground. However, when the series-multiple switch is moved to its high voltage position, as can be seen in FIG. 3B, then terminal 6 of the high voltage winding remains connected to the high voltage bushing, terminal 1 remains connected to ground, terminal 4 is connected to terminal 8 and terminal 3 is connected to terminal 7. This is the series con nection to provide the high voltage setting.

Referring now to FIG. 4 of the drawings, there is shown schematically the multiple primary windings of the transformer. As can be seen from FIG. 4, the primary winding of the transformer comprises three windings; the first having terminals 1, 2 and 7, and the second being provided with terminals 3 and 4 and having the tap changer 30 connected between terminals 3A and 4A of the winding. The third winding comprises the terminals 8, 5 and 6.

Referring to FIG. 5A the connections of the primary windings may be seen when the tap changer is in one position and when the series-multiple switch is in the low position, as is indicated in FIG. 3A of the drawings. As can be seen terminals 1, 3 and 5 are connected together and terminals 2, 4 and 6 are connected together, and the tap changer remains between terminals 3A and 4A. In this manner, as can be seen, the three portions of the primary winding are connected in parallel; the portion of the winding between terminals 1 and 2, the portion of the winding between terminals 3 and 4, and the portion of the winding between terminals 5 and 6. With each of these portions of the windings being rated the same, such as for example, 2400 volts it will be seen that the transformer is connected for a 2400 volt operation.

Referring now to FIG. 5B of the drawings, the connections of the windings are shown when the seriesmultiple switch is in its high voltage position and when the tap changer is still in its one position. As can be seen terminal 7 is connected to terminal 3 while terminal 4 is connected to terminal 8. In this series connection it will be seen that all portions of the primary winding are connected in series thereby providing the highest voltage rating to the transformer. For example, consider this voltage rating as 7970 volts. As is shown the tap changer is still connected between terminal 3A and terminal 4A.

In FIG. 5C the winding connections are shown when the series-multiple switch is still in its high position and the tap changer has been moved to its 2 position. Here as shown, the tap changer is now between terminals 3A and terminal 4B of winding 34. Therefore, the portion of the winding between terminals 4A and 4B has been cut out thereby lowering the over-all voltage of the transformer. In one type of transformer, for example, reducing the transformer voltage to only 7200 volts instead of the 7970 volts which would be possible with the FIG. 5B connection.

From the above it will be readily apparent that were the tap changer moved from its 1 position to its 2 position when the series-multiple switch were in the low position that the winding having terminals 3 and 4 would no longer be, for example, a 2400 volt winding but would have only 1630 volts. Obviously, with a 1630 volt winding connected in parallel with two 2400 volt windings there is effectively a short circuit condition, inasmuch as terminal 6 of one potential would be connected to terminal 4 of another potential. Obviously such a short circuit condition could seriously damage the transformer and if maintained for any length of time may completely destroy the windings of the transformer. Thus in order to provide the desired dual voltage rated transformer with two separate high voltage ratings it is necessary that means be provided to prevent the tap changer from being moved to the wrong position when the transformer is set for the low voltage rating. As has been previously described, with reference to FIG. 1, by means of the interlock between the series-multiple switch and the tap changer, when the series-multiple switch is in the low voltage position the tap changer is moved to the proper position, if not there, and is held in such position. Thus when the series-multiple switch is in the low voltage position the tap changer is in its 1 position and may not be moved to the 2 position. However, when the series-multiple switch is moved to the high voltage position then the tap changer may be moved either to the 1 or the 2 position according to the desired high voltage rating for the transformer.

Obviously, while throughout this specification reference has been made to a two position tap changer, more positions could be provided, if desired. Further, it will be apparent that the handles of the series-multiple switch and the tap changer could be side-by-side if desired, with the interlock horizontal instead of vertical, 2

While there has been shown and described the present preferred embodiment of the interlock means between the series-multiple switch and the tap changer, it will be understood by those skilled in the art that various modifications may be made, that various tap changers and series-multiple switches may be utilized, as desired, without departing from the spirit and scope of the invention as is set forth in the appended claims.

What is claimed as new and which it is desired to be secured by Letters Patent of the United States is:

1. In a transformer having a multiple primary winding, a series-multiple switch mounted in said transformer and electrically connected to said multiple winding, said switch having one position electrically connecting said multiple winding in parallel for low voltage operation and having a second position for electrically connecting said multiple winding in series for high voltage operation, a tap changer mounted in said transformer and electrically connected to said multiple winding, said tap changer having a given position for low voltage operation and being movable to electrically change the turns operative in one portion of said multiple winding for high voltage operation only, and interlocking means interconnecting said series-multiple switch and said tap changer, said interlocking means locking said tap changer in said given position when said series-multiple switch is in said one position and said inter Iockingmeans unlocking said tap changer when said seriesmultiple switch is in said second position.

2. A transformer having a multiple primary winding, a series-multiple switch mounted in said transformer and electrically connected to said multiple winding, said switch having a first position electrically connecting said multiple winding in parallel for low voltage operation and having a second position for electrically connecting said multiple winding in series for high voltage operation, a tap changer mounted in said transformer and electrically connected to said multiple winding, said tap changer having one position for low voltage operation and being movable to at least another position to electrically change the turns operative in one portion of said multiple winding for high voltage operation, interlocking means interconnecting said series-multiple switch and said tap changer, said interlocking means being fixed to said series-multiple switch and movably connected to said tap changer, said interlocking means locking said tap changer in said one position when said series-multiple switch is in said first position, and said interlocking means unlocking said tap changer when said series-multiple switch is in said second position.

3. A transformer as claimed in claim 2, in which said interlocking means comprises an arm member having one end fixed to said series-multiple switch, the opposite end of said arm member being movably connected to said tap changer.

References Cited by the Examiner UNITED STATES PATENTS 2,046,979 7/36 Turner 20050 2,904,649 9/59 Ransom 200-50 BERNARD A. GILHEANY, Primary Examiner. 

1. IN A TRANSFORMER HAVING A MULTIPLE PRIMARY WINDING, A SERIES-MULTIPLE SWITCH MOUNTED IN SAID TRANSFORMER AND ELECTRICALLY CONNECTED TO SAID MULTIPLE WINDING, SAID SWITCH HAVING ONE POSITION ELECTRICALLY CONNECTING SAID MULTIPLE WINDING IN PARALLEL FOR LOW VOLTAGE OPERATION AND HAVING A SECOND POSITION FOR ELECTRICALLY CONNECTING SAID MULTIPLE WINDING IN SERIES FOR HIGH VOLTAGE OPERATION, A TAP CHANGER MOUNTED IN SAID TRANSFORMER AND ELECTRICALLY CONNECTED TO SAID MULTIPLE WINDING, SAID TAP CHANGER HAVING A GIVEN POSITION FOR LOW VOLTAGE OPERATION AND BEING MOVABLE TO ELECTRICALLY CHANGE TE TURNS OPERATIVE IN ONE PORTION OF SAID MULTIPLE WINDING FOR HIGH VOLTAGE OPERATION ONLY, AND INTERLOCKING MEANS INTERCONNECTING SAID SERIES-MULTIPLE SWITCH AND SAID TAP CHANGER, SAID INTERLOCKING MEANS LOCKING SAID TAP CHANGER IN SAID GIVEN POSITION WHEN SAID SERIES-MULTIPLE SWITCH IS IN SAID ONE POSITION AND SAID INTERLOCKING MEANS UNLOCKING SAID TAP CHANGER WHEN SAID SERIESMULTIPLE SWITCH IS IN SAID SECOND POSITION. 